Reproduction in Animals
Focused last-minute revision notes with clear concepts, exam traps, key comparisons and compact practice.
Chapter Snapshot
- Reproduction ensures continuity of a species.
- Sexual reproduction involves male and female gametes.
- The male gamete is sperm; the female gamete is ovum or egg.
- Fusion of gametes is fertilisation, producing a zygote.
- Internal fertilisation occurs inside the female body; external fertilisation occurs outside, commonly in water.
- The zygote divides to form an embryo; later development produces a foetus in mammals such as humans.
- Animals may be viviparous or oviparous.
- Frogs undergo metamorphosis from tadpole to adult.
- Hydra can reproduce by budding; Amoeba by binary fission.
What You Will Learn
- Explain sexual reproduction and gametes
- Identify basic human reproductive organs
- Define fertilisation and zygote
- Differentiate internal and external fertilisation
- Explain embryo and foetus development
- Distinguish viviparous and oviparous animals
- Explain metamorphosis
- Describe budding and binary fission
Last-Minute Chapter Map
Animal reproduction includes sexual reproduction with fertilisation and asexual methods in some organisms.
1. Why Reproduction Matters
Reproduction is the biological process by which organisms produce new individuals of their own kind. It does not keep one individual alive, but it ensures continuity of the species.
2. Sexual Reproduction
Sexual reproduction involves specialised reproductive cells called gametes. The male gamete is the sperm and the female gamete is the ovum (egg). Their fusion combines genetic material from two parents.
3. Human Reproductive Systems
The male reproductive system includes testes, sperm ducts and penis. Testes produce sperm. The female reproductive system includes ovaries, oviducts, uterus and vagina. Ovaries produce ova.
4. Fertilisation
Fertilisation is fusion of a sperm and ovum, forming a zygote. In humans, fertilisation normally occurs inside the female reproductive tract, so it is internal fertilisation.
5. Development of Embryo
The zygote divides repeatedly to form an embryo. In humans, the embryo implants in the uterus and develops. At a later stage, when major body features are recognisable, it is called a foetus.
6. Internal and External Fertilisation
Humans, birds and many land animals show internal fertilisation. Frogs and many fish release gametes into water, where fertilisation may occur externally. External fertilisation often involves production of many eggs because survival chances are lower.
7. Oviparous, Viviparous and Metamorphosis
Oviparous animals lay eggs; viviparous animals give birth to young ones. A frog develops through egg → tadpole → adult, showing metamorphosis, a major change in body form during development.
8. Asexual Reproduction
Asexual reproduction involves one parent and no fusion of gametes. Hydra forms a bud that grows and separates. Amoeba divides into two daughter cells by binary fission.
Internal vs External Fertilisation
| Feature | Internal | External |
|---|---|---|
| Place | Inside female body | Outside body |
| Examples | Humans, birds | Frogs, many fish |
| Gametes / protection | Usually fewer gametes and more protection | Often many gametes with less protection |
Exam Focus
Must Revise Before the Exam
- Sperm and ovum
- Male/female reproductive organs
- Fertilisation
- Zygote, embryo, foetus
- Internal vs external fertilisation
- Oviparous vs viviparous
- Metamorphosis
- Hydra budding
- Amoeba binary fission
Common Mistakes
Key Terms
Key Terms
Quick Revision
Quick Revision
- Sperm + ovum → fertilisation → zygote.
- Zygote divides to form embryo; later mammalian stage is foetus.
- Humans have internal fertilisation.
- Frogs and many fish show external fertilisation.
- Oviparous animals lay eggs; viviparous animals give birth.
- Frog development includes metamorphosis.
- Hydra buds; Amoeba divides by binary fission.
Practice Questions
Fusion of sperm and ovum is called:
A. budding
B. fertilisation
C. metamorphosis
D. germination
View Solution
Correct Answer: B. fertilisation
Fertilisation forms a zygote.
The cell formed immediately after fertilisation is the:
A. foetus
B. zygote
C. bud
D. tadpole
View Solution
Correct Answer: B. zygote
Fusion of gametes produces a zygote.
Which organism reproduces asexually by budding?
A. Hydra
B. Frog
C. Human
D. Hen
View Solution
Correct Answer: A. Hydra
Hydra forms buds that grow and detach.
A frog changes from tadpole to adult by:
A. pollination
B. metamorphosis
C. threshing
D. fission
View Solution
Correct Answer: B. metamorphosis
The major developmental transformation is called metamorphosis.
Differentiate zygote, embryo and foetus.
View Solution
Zygote is the single cell after fertilisation; repeated divisions form the embryo; a later stage with recognisable body structures is called a foetus.
Why do many externally fertilising animals produce large numbers of eggs?
View Solution
Gametes and early young receive less protection outside the body, so producing many increases the chance that some survive.
A newly observed animal lays eggs but fertilisation occurs inside the female. Is it oviparous or viviparous?
View Solution
It is oviparous because classification depends on laying eggs; internal fertilisation can still occur in oviparous animals such as birds.
Chapter Summary
Chapter Summary
- Sperm + ovum → fertilisation → zygote.
- Zygote divides to form embryo; later mammalian stage is foetus.
- Humans have internal fertilisation.
- Frogs and many fish show external fertilisation.
- Oviparous animals lay eggs; viviparous animals give birth.
- Frog development includes metamorphosis.
- Hydra buds; Amoeba divides by binary fission.